Hi Amund,
Are the distances from GND1-Signal the same as Signal-GND2 i.e. is the Signal layer equidistant between the two GND layers? If so, broadly speaking, half of the field is going to be between GND1 and signal and the other half will be between GND2 and signal. If the signal layer is biased towards one or the other GND layer then you'll have proportionally more field on one side than the other. This isn't ideal but every layout is a compromise. Provided you can via through from GND2 to GND1 at either side of the split this should keep the return path controlled. It will still result in an impedance discontinuity which could cause signal integrity issues. There's also the strong possibility of crosstalk from the high speed lines onto the GND2 trace they are crossing. Questions you need to ask yourself include what is this trace and where does it go? Is it filtered at any point? If GND2 is an internal layer then additional emissions should be minimal provided GND1 remains solid. HTH James James Pawson EMC Problem Solver Unit 3 Compliance EMC Testing / Design for EMC / Problem Solving / Pre Compliance / Consultancy / Environmental & Vibration <http://www.unit3compliance.co.uk/> www.unit3compliance.co.uk 07811 139957 2 Wellington Business Park, New Lane, Bradford, BD4 8AL From: Amund Westin <am...@westin-emission.no> Sent: 18 March 2020 08:38 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Stripline - discontinuity in adjacent ground planes Let's say, part of a pcb stack looks like this --- GND1 - SIGNAL - GND2 GND1 is solid copper fill SIGNAL layer consists of high frequency lines LVDS, USB3.0, etc. GND2 should be solid copper fill, but some traces are in that layer due to space utilization reason. These traces are crossing 90 degrees the traces in SIGNAL layer. These traces in the GND2 will create gaps and therefore problems for the return current for the high frequency lines I SINAL layer. But does it matter, as long as the GND1 layer is 100% filled, and there is no disruption of the return current path for the traces in the adjacent SIGNAL layer? Best regards Amund Westin - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
